Plasmons in two-dimensional electron systems with infinite and semi-infinite metal gratings

TL;DR

This paper analytically explores plasmon modes in 2D electron systems with metal gratings, revealing conditions for localized Tamm plasmon modes near the grating edge and their dependence on gate width and wave vector.

Contribution

It introduces the existence and properties of Tamm plasmon modes in 2D electron systems with semi-infinite gratings, highlighting the influence of gate width on mode localization and frequency gaps.

Findings

Tamm plasmon modes can exist in the gaps of the plasmonic band structure.

The mode's frequency depends on the width of the last gate.

Localized modes exist only for finite wave vectors when the last gate is wider.

Abstract

We analytically investigate the plasmons propagating in a homogeneous two-dimensional (2D) electron system, along the metal grating in the form of a periodic array of strip-shaped electrodes (gates) in the vicinity of the 2D system. We show that in the case of semi-infinite grating, the Tamm plasmon modes localized near and propagating along the grating edge can exist in the gaps of the plasmonic band structure provided that the last gate differs in width from the other gates. When the last gate is wider, the spectrum of the fundamental Tamm plasmon mode lies in the lowest frequency gap, below the first plasmonic band. Importantly, we find the mode to exist in this case only for finite values of the wave vector along the grating. Otherwise, if the width of the last gate is smaller, the Tamm plasmon modes occupy higher frequency gaps, and delocalized plasmons from the first frequency band become the lowest frequency excitations.